The present invention relates to a hand pump, and more specifically to an improved structure of handle pump which is durable in use, and which can easily be assembled.
A regular hand pump as shown in FIG. 1, comprises a cylindrical casing 10 having an air outlet 11 at its closed bottom end, a top cover formed of two symmetrical cover plates 12 and 13 and covered on the top opening of the cylindrical casing 10, a handle 20 inserted through the center hole at the top cover of the cover plates 12 and 13, a piston 22 fixedly fastened to the bottom end of the handle 20 by a lock nut 23 and moved up and down inside the cylindrical casing 10, and an O-ring 221 mounted on the periphery of the piston 22 and disposed in contact with the inside wall of the cylindrical casing 10. The handle 20 has a recessed chamber 24 at its top side, which is covered with a cap 26 to hold a needle nozzle 25 on the inside, and two longitudinal deep grooves 21 bilaterally disposed along its length. When pulling the handle 20. upwards, air passes through the longitudinal deep grooves 21 into the inside of the cylindrical casing 10, enabling the handle 20 to be conveniently pulled up. This structure of hand pump has drawbacks. Because the longitudinal deep grooves 21 have a certain depth, the handle 20 tends to be forced to bend due to a concentration of stress. Another drawback of this structure of hand pump is that the longitudinal deep grooves 21 can not guide in sufficient air when the handle 20 is pulled upwards in a rush, and the piston 22 will receive a downward pressure when moved upwards. Still another drawback of this structure of hand pump is that a hand tool must be used when fastening the lock screw 23 to the handle 20 to fix the piston 22 and the handle 20 together. Furthermore, the installation of the cover plates 12 and 13 is also complicated.